Concentration of chemical liquors



May 6, 1958 A. E. REINERT Re- 24,469

CONCENTRATION oF CHEMICAL LIQUoNs Original Filed Jan. 9, 1952 I/ m\ w WQNNos Swlhwm ,mmm-j me a QNl) f INVENTCIL I? -BY 62' Re. 24,469 Reissued May 6, 1958 CONCENTRATION F CHEMICAL LIQUORS Armin E. Reinert, Shawano, Wis., assignor to Herbert H. Clark, Oshkosh, Wis.

Original No. 2,780,281, dated February 5, 1957, Serial No. 265,700, January 9, 1952. Application for reissue November 12, 1957, Serial No. 696,895

2 Claims. (Cl. 159-48) Matter enclosed in heavy brackets [1 appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

The present invention relates generally to improvements in the art of treating solid bearing liquids in order to remove excess liquid from the solutions, and relates more specifically to an improved method and/or system for concentrating sulphite liquor produced bythe sulphite process in paper pulp mills.

The primary object of my invention is to provide an economical and eicient method of concentrating sulphite liquor with the aid of an automatically functioning system composed of simple apparatus. n

VThe concentration and disposal of spent sulphite liquor from paper pulp mills utilizing the sulphite processV of manufacturingv paper has heretofore been a major problem, and while many different methods and types of evaporators and concentrators have heretofore been proposed and tried experimentally and to some extent commercially, none of these have proven entirely satisfactory. These waste sulphite liquors are discharged from the pulp mills in large quantities and at high temperature approximating the boiling point of water, and contain from ten to fifteen percent of solids in suspension, thus `causing very objectionable contamination of rivers and streams if the fresh liquor is deposited directly therein. While it is not essential that the concentration be continued until all of the liquid has been removed and dry solids result, it is desirable to remove the greater proportion of the liquid ingredients of the sulphite liquor and to discharge the concentrated residue or solid ingredients at vastly reduced temperature preparatory to final disposal thereof.

- It is therefore an important object of the present invention to provide an improved process of effectively removing excess liquid from spent sulphite liquor, and for delivering the concentrated solid constituents in readily disposable condition.

Another important object of the `invention is to provide a method of commercially concentrating sulphite liquor byfrefrigeration, sublimation, and pressure application in a continuous and eiective manner.

A further important object of my invention is to provide an improved spent paper mill liquor concentrating system utilizing relatively standard equipment assembled so as to constantly treat large volumes of the liquid in an economical and effective manner.

Still another important object of this invention is to provide a closed circuit system for removing excess liquid from sulphite liquor from paper pulp mills, and wherein the yexcess liquid in cool condition is `utilized to initially reduce the temperature of the fresh liquor.

An additional object of the invention is to provide a simple and relatively inexpensivesystem for effecting concentration of sulphite liquor to any desired degree regardless of tluctuations in the supply and variations in the proportions of the ingredients.

These and other objects and advantages of my invention will be apparent from the following detailed description.

A clearer conception of the severalsteps involved in the improved method, and of the construction and functioning of a commercial system involving this method,

may be had by referring to the drawing accompanying and forming a part of this specification wherein the various parts are identified both by name Aand by suitable reference characters.

The single gure of the drawing is a diagram depicting a typical commercial embodiment of a system for continuously exploiting the improved method of concentrating sulphite liquor delivered theretol in heated condition from the paper or pulp mill.

-While only one typical assemblage of apparatus adapted to deliver the nal product in liquid but highly concentrated condition, has been shown and described by way of illustration, it is not the intention to unnecessarily restrict the use of the particular apparatus illustratedy by virtue of this limited showing; and it is also contemplated that specific descriptive terms employed herein be given the broadest possible interpretation consistent with the disclosure.

Referring to the drawing, the typical system diagram illustrated, comprises in general, a rubber lined tank 2v having a fresh and hot sulphite liquor inlet 3 near its medial portion and being provided at its upper end with a vapor outlet 4 and its lower end with an initially cooled liquor discharge conduit 5; a barometric or similar condenser 6 communicating with the supply tank outlet 4 and having a cooling water inlet pipe 7 and a vacuum producer 8 associated with its upper end while its lower.

portion is provided with the usual tail pipe 9; a centrifugal pump 10 for receiving liquid from the tankdischarge conduit 5 and for delivering this initially cooled liquid through another conduit 11 into ra high pressure hydraulic pump 12 having a discharge line 13; a heat exchanger or refrigerator 14 cooperating with the high pressure line 13 to materially reduce the temperature of the liquid ilowing therethrough; a housing 15 forming an enlarged closed chamber 16, and a spray nozzle 17 at the delivery end of the high pressure line 13 within the chamber 16 adjacent to one end wall of the housing 15; an induced draft fan 18 adjacent to the opposite end wall of the housing 15 for removing vapors separated by sublimation within warmer portions ofthe chamber 16 and for urging these -vapors through a second heat exchanger 19 adapted to admit cool fresh air to the chamber 16 through an air duct 20 and the refrigerator 14; a series of hoppers 21 at the bottom of the chamber 16 each having a pair of cooperating press rolls 22 therebelow; a concentrated liquor receiving tank 23 located.

below the press rolls 22 and having therein an endless perforated conveyor 24 for separating the solid ice delivered by the rolls from the treatedliquor; ya trough 25 f` at the delivery end of the conveyor 24 having suitable controls for liquid delivered therefrom; and a centrifugal pump 26 for withdrawing ice cold water from the trough 25 and for transporting this liquid through the pipe 7. The rubber lined tank 2 is preferably formed of steel vor other suitablemetal, and the condenser 6 may be of the barometric or any other suitable type adapted to create a high degree of vacuum within the tank 2 and to condense and constantly remove the vapors rising from the the pump 26 through the supply pipe 7, and that the vapors are rapidly removed from the tank 2 without applying heat and thereby eliminating scaling, the temperature :of the fresh liquor admitted at the inlet 3 is promptlyAA reduced from approximately 220 F. to somewhat below atmospheric temperature.

The centrifugal pump is operable to constantly transfer the initially cooled sulphite liquor from the conduit 5 through the conduit 11 into the high pressure hydraulic pump 12 which should preferably be or a type adapted to deliver the liquor at a pressure 1n excess of two thousand pounds per square inch to the refrigerator 14 through the spray pipe 13. The refrigera tor may be operated by ammoniaor any other type of refrigerant admitted in liquid form through a lower inlet 28 and discharged in gaseous condition through an upper outlet 27, and this refrigerator 14 should be adapted to somewhat lower the temperature of the liquid flowing through the line 13 to the spray nozzle 17, and to also lower the temperature of the fresh pre-cooled air admitted through the duct 20 considerably below water freezing temperature and preferably to about 20" F.

The refrigerated fresh air is delivered from the heat exchanger 14 into the chamber 16 around the spray nozzle 17 and the housing 15 should preferably be formed of wood or other relatively good insulation so as to pre-` vent excessive heating of the upper portion of the chamber 16 wherein the nozzle 17 converts the sulphite liquor into snow. The hoppers 21 at the bottom of the housing 15 need not be so well insulated so that somewhat warmer temperatures will exist therein and will remove considerable moisture from the snow by sublimation. This moisture is withdrawn from the chamber 16 by the exhaust fan 18 and is condensed in the heat exchanger 19 from which the liquid of condensation is discharged through adrain 30 while the gases escape through a stack 31. Fresh cool air may be admitted to the heat exchanger 19 through an inlet 32 and is delivered thereby through the duct 20 to the refrigerator 14.

The hoppers 251 are adapted to receive the snow delivered from the nozzle 17 and by the cold air from the refrigerator 14 as shown, and the press rolls 22v should be constantly operated to simultaneously com press the snow flakes into solid ice particles and to express the residual sulphite liquor from the ice. The perforated endless conveyor 24 should be located within the sulphite liquor collecting tank 23 with the upper conveyor run directly beneath the press rolls 22 and 'conconcentrated sulphite liquor will drop into the tank 23 and may be withdrawn through the lower tank outlet' 33 while the solid ice particles will be discharged overi a chute 34 into the trough 2S. The ice `particles will contain only pure water but may have some solid ingredients of the sulphite liquor adhering to the surface thereof, and these may be washed oi into the tank 23 by fresh water delivered through a nozzle 35 before they reach the chute 34.

'The trough 25 should be kept supplied with an abundance of water the temperature of which will be constantly reduced to approximately 32 F. bythe ice cubes or particles delivered thereto by the conveyor 24, and the centrifugal pump26 should be continuously operated and controllably fedy from Vthe trough so as to deliver an abundant supply of ice cold water through thepipe 7 to the barometric condenser 6. The vrefrigerator 14 and the several ypumps thus function to keep the con'- denser 6 operating at maximum eciency and to reduce the degree of refrigeration required toa minimum, byy

to effect continuous exploitation'of the improved method of concentrating the sulphite liquor, should be clearly apparent from the foregoing description of the constrution and operation of the apparatus; and While the various pumps, heat exchangers and other elements are stand ard and readily available equipment lthey must neces= sax-ily cooperate in a particular manner in order to obtain the desired results. While the concentrated liquor is still in liquid form with its percentage of solid constituents considerably increased upon a single pass through the system, the liquid content may be substantially eliminated by subjecting the product ofthe rst concentration to further treatment in one or more successive similar systems or special evaporators.

From the foregoing detailed description it will be ob- `i vious that my improved method is not only highly ellicient mum economy of operation results.

It should be understood that it is not desired to limit this invention to the exact steps of the method or to the precise apparatus for exploiting the method herein specifically described and shown, for vario-us modifications with-` in the scope of the appended claims may occur to persons skilled'in the art.

I'claim: l 1. The method of continuouslyl concentrating spent hot sulphite liquor delivered from paper mill digesters and which contains excess water, which method comprises,

initially subjecting the hot liquor to a partial vacuum to remove some of the excess water in-the form of vapor, thereafter subjecting the'partially'dehydrated liquor to high pressure and to low temperature and spraying the same through a restricted orifice into a connedspace to convert the liquor into snowy containing congealed wa? ter and concentrated sulphite liquid, mechanically lseparating the congealed water from the concentrated sulphite liquid, heat treating the congealed water toconvert -it into or the original patent UNITED STATES PATENTS l 981,860 Jackson lan. l7, 19ll 1,273,208 Weil v.- July 23, 1918 1,976,204 Voorhees v Oct. 9, l934v 2,009,283 Warner 4 July 23, 1935 2,312,474 Peebles Mar. 2, 1943 2,411,152 Folsom Nov` 19,J 1946 y2,471,035 Hurd iMay 24, 1949 2,533,125 Levinson e't al. Dec. 5, l950 2,542,041 Mason et al. Feb. 2o, 1951 2,556,250 Baumanl June-l2, 195i 2,595,852" Hopper k l s v l z May 6, 1952, f Foluarcul PATENTS l 243,982 Great Britain-- l.v Dec. l0, i925 A cold liquid water, and condensing the vapor initially removed from the hot liquor by subjecting said vapor inI mining water and which is derived from paper mill digesters or the like, which method comprises, initially subjecting the liquor to vacuumV to remove som-c of the water 'in the' form of vapor, vthereafter subjecting the partially'dehydrated liqiior'to pressure and to temperature below 32 F. ind injecting 'the same through -restr'icted orifice into aconfined space tof'convert thel liquor into snow containing congea'led water and concentrated chem'- ica'l liquid, separating the congealed water from tlte'con- .centrated chemical liquid, converting the separated conwater derived from said congealed water.

References Cited in the ytile of this patent 

